Touch and Beyond: Mapping the Evolution of Silver Nanowire Transparent Conductors

In the past five years, silver nanowire-based transparent conductor materials have become one of the most popular approaches to replace the incumbent indium tin oxide (ITO) technology. In a nutshell, Ag NW TCs offer high transmission of light (>90%) with low resistance (sub-100 Ω/square) which has been a sweet spot for, initially, touch panel applications. Self-assembling silver nanostructures have already proven themselves in that touch-sensor market, and must now be thought of as an established TC option.

We note, though, that Ag NWs currently are on the verge of some interesting transformations. In some ways the addressable market for this kind of TC is expanding — it seems well-suited, for example, to the curved TV displays that came onto the market a year or so back. At the same time, recently announced R&D is improving the performance of AG NW TCs, so that these coatings are pursuing more market inroads at the expense primarily of ITO, but also other alternatives such as metal meshes.

Big Stretch: Widening the Touch Market

Touch is the core functionality in the sea of smartphone and tablet products on the market, even low-end versions. Indeed, their ubiquity arguably wouldn’t have happened without the rise of improved touch-panel functionality, begun with Apple’s iPhone and now adopted by all the major phone and electronics device suppliers. Windows 8 also has made touch a central part of the PC story, although not all notebooks, laptops and desktops actually implement touch.

Virtually all suppliers of non-ITO TCs have targeted the touch sector as their first revenue path. In fact, the touch-screen business is more open to new TCs than any other TC-using sector, although it still relies heavily on ITO (we estimate 10-15 percent of touch-screen sensors used alternative TCs in 2014). That penetration number can only continue to grow as touch sensing becomes increasingly common for displays.

Ag NWs have made their bones for smaller devices (tablets and cell phones) particularly against ITO, in part due to the aforementioned conductivity and transmission, but also because some of its processes are simpler and lower-cost, such as room-temperature laser processing and no need for consumables such as photoresist, etchants, or strippers.

Interestingly, the major Ag NW suppliers all claim now to be gaining traction in larger touch-panel products, the domain of sibling rival metal mesh: larger tablets, laptops, all-in-one PCs, kiosks and larger displays, all the way up to and exceeding 70″. Cima Nanotech recently debuted in the U.S. a 57-inch interactive multitouch tabletop and a 42-inch digital signage touchscreen, while Carestream has shown a 42-in. touchscreen gaming device. (For what it’s worth, we also are seeing metal mesh suppliers push their way into smaller-display devices as well.)

Seeking Markets Outside Touch

Manufacturers of Ag NW TCs are beginning to recognize that touch sensors are not necessarily the gift that keeps on giving.  Not only are there natural limits to how far the touch display paradigm can be pushed — who really wants a touch-controlled TV? — but it is likely that eventually gesture control and other human computer interfaces (HCI) will take some of the bloom off the touch markets. These dangers are well understood by all the firms in the TC space, including those that base their products on silver nanomaterials.

As a result, Ag NW firms are beginning to turn their attention to other markets, some new and some familiar. One of these is solar photovoltaics (PV), although some Ag NW firms have long dabbled in PV so one could view this rather re-turning their attention to it. The PV sector is not the business it once was, though, so any (re-)entry strategies for TC firms will have to be crafted very carefully.

Next Stop, Flexible Electronics and Wearables:  Other R&D suggests where the future of Ag NW TCs may lead, and in many cases this points to flexible and wearable electronics — an application area in which Ag NWs (or any TC alternative) would be free of competition from ITO.

•    Researchers from the Singapore Institute of Manufacturing Technology reported on biaxially stretchable Ag NW TCs, showing that a silver nanowire film transfer-printed onto PDMS maintained “good electrical conductivity” when stretched up to 10%. This has some relevance to flexible displays, but is even more important in the context of wearables.

•    Northwestern University researchers have explored cyclic loading to better understand Ag NWs’ fatigue properties, by varying the tension on Ag NWs (<120nm diameter). The results here are especially interesting — they showed permanent deformation was actually partially recoverable, suggesting yet again potential application in flexible electronics.

•    Researchers from North Carolina State University have recently investigated touch sensors made from Ag NW electrodes with interdigitated patterning. Some of that work, though, also relates to flexible substrates.

Business Development and Funding Continues

No matter the market dangers, money keeps rolling in for AG NW, and business development continues in the display sector. Both Cambrios ($10 million) and Cima NanoTech (undisclosed) have secured new funding in the past 12 months, which we think reflects a certain amount of confidence in Ag NW TC solutions in existing markets and beyond.

Samsung Venture Investment’s investment in Cambrios is especially important given the parent group’s prominence in the mobile display business, and the fact that it has had the chance to test drive many different kinds of alternative TCs.  Financial support for the Ag NW business may also be emerging on the speculation that today’s silver nanomaterial TC firms will ultimately find new revenue sources that have nothing to do with TCs.

We are seeing activity today ramp up significantly. Cambrios, for example, claims that its capacity surged from 22,000 liters/year in 2013 to 175,000 liters/year in 2014. Carestream has been ramping production since mid-2014, anticipating a big takeoff for its films and technology; it claims it is making hundreds of millions of square meters of film per year.

Competition, Cooperation, and the Future

Of course, TCs based on metallic nanomaterials must compete with other alternative TCs and ITO; obviously this is an ongoing issue, and often the facts on which they compete are somewhat shadowy, rather a kind of “specsmanship” game.

And yet alternative TCs are not always competitive. We have long suggested hybrid combinations could, and arguably should, emerge among the alternative TC sector. We now have two recent examples of this trend:

– Cambrios and Heraeus announced they will create a new “hybrid one-layer” TC material combining PEDOT:PSS conductive polymers and Ag NWs.

– Carestream and Foxconn subsidiary CNTouch have announced an R&D program to develop touch-screen application targets containing film sensors and modules with both single- and multi-layers of transparent conductive film. It’s not clear if this will combine both Ag NW and carbon nanotube materials, however.

Based on all of the above, n-tech Research remains quite bullish on the future of TCs using silver nanomaterials.  As we suggest, solar panels may be the next place that we start to see real commercialization of these TC materials. Another likely receptive audience is OLED makers, who would actually prefer a non-ITO TC alternative, and especially ones with the properties (including flexibility) that Ag NWs offer.

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